[Qemu-devel] [PATCH v2] linux-user: Handle microMIPS encoding when processing trap exceptions

[Qemu-devel] [PATCH v2] linux-user: Handle microMIPS encoding when processing trap exceptions

[Kwok Cheung Yeung]

Decode trap instructions during the handling of an EXCP_TRAP according to
the current ISA mode.

Signed-off-by: Kwok Cheung Yeung <kcy@codesourcery.com>
---
 linux-user/main.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

v2: Read microMIPS instructions sequentially as 16-bit values to avoid
    endianess issues. Add braces to if statement to conform to formatting
    standards.

diff --git a/linux-user/main.c b/linux-user/main.c
index 7f15d3d..7faa945 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -2372,14 +2372,30 @@ done_syscall:
                 abi_ulong trap_instr;
                 unsigned int code = 0;
 
-                ret = get_user_ual(trap_instr, env->active_tc.PC);
+                if (env->hflags & MIPS_HFLAG_M16) {
+                    /* microMIPS mode */
+                    abi_ulong instr[2];
+
+                    ret = get_user_u16(instr[0], env->active_tc.PC) ||
+                          get_user_u16(instr[1], env->active_tc.PC + 2);
+
+                    trap_instr = (instr[0] << 16) | instr[1];
+                } else {
+                    ret = get_user_ual(trap_instr, env->active_tc.PC);
+                }
+
                 if (ret != 0) {
                     goto error;
                 }
 
                 /* The immediate versions don't provide a code.  */
                 if (!(trap_instr & 0xFC000000)) {
-                    code = ((trap_instr >> 6) & ((1 << 10) - 1));
+                    if (env->hflags & MIPS_HFLAG_M16) {
+                        /* microMIPS mode */
+                        code = ((trap_instr >> 12) & ((1 << 4) - 1));
+                    } else {
+                        code = ((trap_instr >> 6) & ((1 << 10) - 1));
+                    }
                 }
 
                 if (do_break(env, &info, code) != 0) {
-- 
1.8.3.3

Re: [Qemu-devel] [PATCH v2] linux-user: Handle microMIPS encoding when processing trap exceptions

[Peter Maydell]

On 19 July 2013 15:47, Kwok Cheung Yeung <kcy@codesourcery.com> wrote:
> Decode trap instructions during the handling of an EXCP_TRAP according to
> the current ISA mode.
>
> Signed-off-by: Kwok Cheung Yeung <kcy@codesourcery.com>
> ---
>  linux-user/main.c | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
>
> v2: Read microMIPS instructions sequentially as 16-bit values to avoid
>     endianess issues. Add braces to if statement to conform to formatting
>     standards.

This code looks OK but last time round I asked about
EXCP_BREAK -- why doesn't that also need to change?

thanks
-- PMM

Re: [Qemu-devel] [PATCH v2] linux-user: Handle microMIPS encoding when processing trap exceptions

[Kwok Cheung Yeung]

On 19/07/2013 3:52 PM, Peter Maydell wrote:
> On 19 July 2013 15:47, Kwok Cheung Yeung <kcy@codesourcery.com> wrote:
>> Decode trap instructions during the handling of an EXCP_TRAP according to
>> the current ISA mode.
>>
>> Signed-off-by: Kwok Cheung Yeung <kcy@codesourcery.com>
>> ---
>>   linux-user/main.c | 20 ++++++++++++++++++--
>>   1 file changed, 18 insertions(+), 2 deletions(-)
>>
>> v2: Read microMIPS instructions sequentially as 16-bit values to avoid
>>      endianess issues. Add braces to if statement to conform to formatting
>>      standards.
>
> This code looks OK but last time round I asked about
> EXCP_BREAK -- why doesn't that also need to change?
>

This patch was intended to fix the handling of floating-point exceptions while 
running the GCC unit tests (gcc.c-torture/execute/20101011-1.c) on microMIPS, 
which only requires EXCP_TRAP to work properly. I'll post a version with 
EXCP_BREAK fixed shortly.

Thanks

Kwok